Sulfolene compounds are generally used as intermediates for the corresponding hydrogenated sulfolane derivatives which are in turn useful as selective solvents, ingredients in pesticidal compositions, and intermediates for other organic chemicals. Sulfolenes are unsaturated five-membered rings of four carbon atoms and a sulfur atom, the latter having two oxygen atoms directly attached thereto. Thus, the generic term "sulfolene" covers the simple unsubstituted sulfolenes, viz., the 2-sulfolene and the 3-sulfolene having the general structures ##STR1## as well as the various substituted derivatives described herein. Sulfolenes are generally prepared by reacting sulfur dioxde with a conjugated diene like 1,3-butadiene. In addition, polymerization inhibitors are sometimes added to reduce the undesirable formation of polysulfone polymers. One such method is described in U.S. Pat. No. 3,514,469 which employs substituted phenols like pyrogallol, tert-butyl pyrocatechol and such amines as phenyl-.beta.-naphthylamine as polymer inhibitors in the synthesis of sulfolene. Thus, the essence of the current invention is to provide an alternate class of compounds, namely the mono- and dialkenyl amines, as inhibitors to reduce the formation of polysulfone polymers in the preparation of sulfolenes. It has also been found that these alkenyl amines do not interfere with subsequent reactions such as hydrogenation which converts the sulfolenes to sulfolanes.
Accordingly, an object of this invention is to provide an improved process for the production of sulfolene compounds.
It is another object of this invention to provide a polymerization inhibitor useful in the synthesis of sulfolenes.
Another object of this invention is to provide a process whereby polymer formation is minimized during the synthesis of sulfolenes.
Other objects, aspects, and the several advantages of this invention will become apparent to one skilled in the art upon reading this disclosure and the appended claims.